Mobility within a packet-switched telephony network

ABSTRACT

According to an embodiment of the present invention, a system is provided that includes a cellular network, a Public Switched Telephone Network (PSTN) and a mobile IP-telephony network (MIPTN). Both the cellular network and the MIPTN include a Home Function and one or more visited Functions. MIPTN subscribers can roam within the MIPTN. Also, a Gateway Function interfaces the PSTN and the MIPTN to allow roaming between the cellular network and the MIPTN. The Gateway Function performs a dynamic mapping function between PSTN/cellular addresses (e.g., in E.164 format) and MIPTN addresses (e.g., IP addresses) to allow registration and call delivery for subscribers roaming between the cellular network and the MIPTN. A similar type of Gateway Function also allows Short Message Service (SMS) messages to be delivered over the MIPTN as well.

CROSS-REFERENCE TO RELATED APPLICATIONS

The subject matter of this application is related to the subject matterof the following applications, all filed on Jun. 21, 1999: Ser. No.09/337,336 entitled “Mobility in Packet-Switched Telephony Networks”;Ser. No. 09/337,328 entitled “Mobility Between IP Telephony Networks andCellular Networks”; Ser. No. 09/337,329 entitled “A Gateway Function ForSupporting Mobility Between Packet-Switched Telephony Networks AndCellular Networks”; and Ser. No. 09/337,335 entitled “Short MessageService Support Over A Packet-Switched Telephony Network.”

BACKGROUND

This application generally relates to packet-switched telephonynetworks, such as IP telephony networks, and to cellular networks, andmore particularly to a technique that allows subscribers to roam betweenan IP-telephony network and a cellular network.

IP-Telephony Networks

Voice or telephony services can now be provided over a packet-switchednetwork, such as the Internet. These packet-switched-telephony networksare commonly referred to as IP telephony networks because the InternetProtocol (IP) is the primary protocol used over the Internet. One IPtelephony standard, for example, is the International TelecommunicationsUnion (ITU) H.323 standard.

FIG. 1 illustrates an example of an IP telephony network, also known asa Voice over IP (VoIP) Network. The VoIP network includes a gatekeeperfunction, one or more gateways and a packet-switched network (e.g., aportion of the Internet).

The gatekeeper function is optional and provides call authorization forboth accepting and placing calls in its zone or area of control. Agatekeeper can also allocate bandwidth, can maintain call detailrecords, and can perform other network management functions.

A packet-switched-telephony gateway bridges a circuit switched networksuch as the Public Switched Telephone Network (PSTN) and apacket-switched network such as an IP network or the Internet. The(standard) IP telephony gateway bridges the PSTN and IP networks toallow phone-to-phone and phone-to-personal computer (PC) multimediacommunications (voice, video and/or data). The IP telephony gatewayprovides the appropriate translation between transmission formats (forexample, H.225.0 of an H.323 endpoint to/from H.221 of an H.320endpoint) and between communication procedures (for example, H.245 of anH.323 endpoint to/from H.242 of an H.320 endpoint). The IP telephonygateway also performs call setup and clearing on both the network sideand the switched circuit network side. Translation between video, audio,and data formats may also be performed in the gateway. In general, thepurpose of the IP-telephony gateway is to complete the call in bothdirections between the network endpoint and the switched circuit networkendpoint in a transparent fashion.

An example of IP telephony gateway is the H.323 gateway (implementingthe ITU H.323 standard). H.323 gateways allow interoperation of H.323systems with other audio/video conferencing systems on IntegratedServices Digital Networks (ISDN), plain old telephone systems (POTS),Asynchronous Transfer Mode (ATM), and other transports. An IP telephonygateway operates as an endpoint on the IP-telephony network thatprovides real-time, two-way communication between IP telephony terminalson the IP-based network and other ITU terminals on a switched-circuitnetwork, or to another IP-telephony gateway. Switched Circuit Networkconnectivity is achieved in the IP telephony context by using gatewaysfor H.320 (ISDN), H.324, H.323, POTS, and other endpoints on othernetworks.

FIG. 1 is a diagram illustrating an example IP telephony network.Referring to FIG. 1, when an incoming call (1) reaches an IP telephonygateway (GW) (here indicated as Originating IP telephony GW), thegateway contacts the gatekeeper it is registered with asking to set up acall towards the dialed number received from the incoming call set uprequest (Access Request, ARQ, 2). The gatekeeper translates the dialednumber (or directory number) into the IP address of the DestinationIP-telephony gateway, i.e. the gateway that has to be reached in orderto reach the final destination of the call, and provides this IP addressto the originating IP telephony gateway (Access Confirmation, ACF, 3).The Originating IP-telephony GW sets up an IP-telephony call over thepacket-switched network or IP network towards the DestinationIP-Telephony GW providing its IP address and the dialed number (Callsetup, 3). The Destination IP-telephony GW contacts the gatekeeper it isregistered with (it may be the same as the Originating IP-telephony GWor a different gatekeeper) asking to accept a call incoming from theOriginating IP-telephony GW (ARQ, 4) and directed towards the dialednumber. If the gatekeeper grants the incoming call to the DestinationIP-telephony GW (ACF, 5), the Destination IP-telephony GW establishesthe PSTN call (call, 7), and then the call is established between thetwo IP-telephony GWs over the IP network (call establishment, 6). Thedestination IP-telephony gateway translates the IP packets into theappropriate format for transmission over the PSTN.

However, IP telephony standards and products are currently defined onlyfor fixed networks. Mobility has not been considered in IP telephony inthe sense that IP telephony subscribers are not allowed to roam betweenIP telephony networks.

For example, a subscriber in one area of the country is registered witha local gatekeeper. If the subscriber moves or travels to another partof the country, the subscriber will not be able to connect to thegatekeeper in the new part of the country because the new gatekeeper hasno information describing the subscriber.

Cellular Networks

In addition, cellular subscribers can roam within cellular communicationsystems. In Global System for Mobile (GSM), a visiting location register(VLR) and a home location register (HLR) are used. The VLR containsrelevant data of all mobile stations currently located in a servingMobile Services Switching Center (MSC). The HLR is a database in chargeof the management of the mobile subscribers. The data stored in the HLRincludes service subscription information and location information (theidentity of the currently serving VLR to enable routing ofmobile-terminated calls).

When a visiting (or roaming) cellular subscriber is detected in aserving system, the location update processes notify the subscriber'sHLR of the subscriber's presence in the serving system. When thesubscriber is detected for the first time, the serving system creates atemporary record for the subscriber storing the service information andthe location information. When the subscriber changes serving areas, therecord in the HLR is simply updated with the new location information.In both cases the HLR is notified. When the HLR is notified by theserving system, it updates the location information in the subscriber'srecord. If the location information is different from the one previouslystored in the record, the HLR cancels the subscriber's location in theprevious serving system.

If subscriber B is roaming in a serving cellular system and a party Adials subscriber B's directory number, the call is routed through thePSTN to the home system of subscriber B. The MSC in the home system thatreceives the incoming call contacts subscriber B's HLR to determine howto route the call. The HLR determines that the call is for subscriber Band issues a request to subscriber B's current serving system for theinformation to route the call. The serving system allocates a telephonenumber (often called Roaming Number or RN) temporarily assigned tosubscriber B to route the call and provides the RN to the HLR. The HLRprovides the RN to the MSC in the home system, which in turn routes thecall to the RN through PSTN. When the serving system receives theincoming call, it associates it with subscriber B based on the RN, andpages the subscriber B.

However, IP-telephony networks presently do not permit roaming ormobility within the IP-telephony network. Also, cellular networks andIP-telephony networks are distinct and incompatible networks and do notallow for roaming between cellular and IP-telephony networks.

Short Message Service (SMS)

As provided in Global System For Mobile Communications (GSM), ShortMessage Service (SMS) gives cellular network subscribers the ability tosend and receive short text messages. Short messages usually containabout one page of text or less. Some systems limit the short message to160 alphanumeric characters. However, there is presently no provisionfor delivering short messages over an IP-telephony network, or fordelivering short messages to subscribers roaming between a cellularnetwork and an IP-telephony network.

Therefore, a need exists for a technique that allows subscribers to roamwithin an IP-telephony network, to roam between an IP telephony networkand a cellular network, and for the delivery of short messages over anIP-telephony network.

SUMMARY OF THE INVENTION

According to an embodiment of the present invention, a system isprovided that includes a cellular network having a cellular HomeFunction which may include a Gateway Mobile Services Switching center(GW MSC) and a Home Location Register (HLR), and one or more cellularVisited Functions, each cellular Visited Function may include a VisitedLocation Register(VLR) and a MSC. The system also includes a MobileIP-Telephony Network (MIPTN), including a MIPTN Home Function and one ormore MIPTN Visited Functions.

The system also includes a Public Switched Telephone Network (PSTN) thatis connected to the cellular network. The PSTN is also connected to theMIPTN via a Gateway Function that provides mobility support, includingthe storage of dynamic mappings obtained during registration.Alternatively, the Gateway Function interfaces the cellular network andthe MIPTN directly.

According to an embodiment of the present invention, a technique isprovided to allow roaming or mobility within an IP-telephony network(MIPTN). A subscriber registers with a Visited Function where thesubscriber is located. The Visited Function then sends a message to thesubscriber's MIPTN Home Function to provide updated subscriber locationinformation. When a call is received that is intended for thesubscriber, the IP address (or transport address) of the serving MIPTNVisited Function where the subscriber is registered (or located) isretrieved from the MIPTN Home Function. An IP-telephony call is then setup towards the IP address of the serving MIPTN Visited Function.

According to another embodiment of the present invention, a GatewayFunction is provided that supports mobility or roaming between a MobileIP-telephony Network (MIPTN) and a cellular network. When a cellularsubscriber roams to the MIPTN, or when a MIPTN subscriber roams to thecellular network, the subscriber's Home Function and Visited Functionwill be located in different types of networks. The cellular network andthe MIPTN are distinct and incompatible networks because different typesof messages, signaling and addressing systems are used. The GatewayFunction performs the interworking between the PSTN/cellular messageformats and signaling and those in the MIPTN. In particular, the GatewayFunction supports internetwork roaming by storing a dynamic mapping orcorrespondence between a subscriber identification (e.g., IMSI orMSISDN) and an address of a Visited Function where the subscriber hasroamed. This dynamic mapping or correspondence is stored by a GatewayFunction during the subscriber registration process when cellularsubscribers roam to the MIPTN, or when MIPTN subscribers roam to thecellular network. This dynamic mapping stored in the Gateway Functionallows the subsequent delivery of calls or SMS short messages via theGateway Function to a subscriber that is roaming between networks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of an IP telephony network.

FIG. 2 is a block diagram illustrating an example system architectureaccording to an embodiment of the present invention.

FIG. 3 is a block functional diagram illustrating a Mobile IP-telephonynetwork Home Function according to an example embodiment of the presentinvention.

FIG. 4 is a functional block diagram illustrating a Mobile IP-telephonynetwork Visited Function according to an example embodiment of thepresent invention.

FIG. 5 is a functional block diagram illustrating a Mobile IP-telephonynetwork Gateway Function according to an example embodiment of thepresent invention.

FIG. 6 is a diagram illustrating an example subscriber registration fora Mobile IP-Telephony subscriber roaming within the Mobile IP-TelephonyNetwork.

FIG. 7 is a diagram illustrating an example subscriber registration fora Mobile IP-Telephony subscriber roaming to a cellular network.

FIG. 8 is a diagram illustrating an example subscriber registration fora cellular network subscriber roaming to a Mobile IP-Telephony network.

FIG. 9 is a diagram illustrating an example call delivery of anIP-telephony call to a Mobile IP-telephony subscriber roaming in aMobile IP-telephony network.

FIG. 10 is a diagram illustrating an example delivery of aPSTN call to aMobile IP-telephony subscriber roaming in the Mobile IP-telephonynetwork.

FIG. 11 is a diagram illustrating an example delivery of an IP-telephonycall to a Mobile IP-telephony subscriber roaming to a cellular network.

FIG. 12 is a block diagram illustrating an example delivery of anIP-telephony call to a Mobile IP-telephony subscriber roaming to acellular network, corresponding to FIG. 11.

FIG. 13 is a block diagram illustrating an example delivery of a PSTNcall to a Mobile IP-telephony subscriber roaming to a cellular network.

FIG. 14 is a diagram illustrating an example delivery of an IP-telephonycall to a mobile cellular network subscriber roaming to an IP-telephonynetwork.

FIG. 15 is a block diagram illustrating an example delivery of anIP-telephony call to a mobile cellular network subscriber roaming to anIP-telephony network, corresponding to FIG. 14

FIG. 16 is a block diagram illustrating an example delivery of a PSTNcall to a mobile cellular network subscriber roaming to an IP-telephonynetwork.

FIG. 17 is a diagram illustrating an example delivery of a short messagefrom a IP-telephony short message service center to a mobile cellularnetwork subscriber that is roaming within the cellular network.

FIG. 18 is a diagram illustrating an example delivery of a short messagefrom a cellular short message service center to a mobile MIPTNsubscriber that is roaming within an IP-telephony network.

FIG. 19 is a diagram illustrating an example delivery of a short messagefrom an IP-telephony short message service center to a mobile cellularnetwork subscriber that is roaming within the IP-telephony network.

FIG. 20 is a diagram illustrating an example delivery of a short messagefrom a cellular network short message service center to a mobileIP-telephony network subscriber that is roaming within a cellularnetwork.

FIG. 21 is a diagram illustrating an example delivery of a short messagefrom a cellular network short message service center to a cellularnetwork subscriber that is roaming within an IP-telephony network.

FIG. 22 is a diagram illustrating an example delivery of a short messagefrom an IP-telephony network short message service center to anIP-telephony subscriber that is roaming within a cellular network.

FIG. 23 is a diagram illustrating an example delivery of a short messagefrom an IP-telephony network short message service center to anIP-telephony subscriber that is roaming within an IP-telephony network.

DETAILED DESCRIPTION

Introduction

According to an embodiment of the present invention, techniques aredisclosed to allow roaming within an IP-telephony network, to allowroaming between an IP-telephony network and a cellular network, and toallow delivery of Short Message Service (SMS) messages over anIP-telephony network. As used herein, an IP-telephony network havingmobility or roaming capabilities is referred to herein as a MobileIP-telephony network (MIPTN).

System Architecture

Referring to the figures in which like numerals indicate like elements,FIG. 2 is a block diagram illustrating an example system architectureaccording to an example embodiment of the present invention. The systemarchitecture includes a Mobile IP-telephony network (MIPTN) 202, aPublic Switched Telephone Network (PSTN) 240 and a cellular network 260.Cellular network 260 may be for example, a Global System for MobileCommunications (GSM) network, or other cellular network.

The MIPTN 202 includes a MIPTN Home Function 204, one or more MIPTNVisited Functions (including MIPTN Visited Functions 206 and 208), and aGateway Function 210. The MIPTN Home Function 204 stores subscriberprofiles for MIPTN subscribers, receives and stores updated locationinformation for MIPTN subscribers from Visited Functions. The MIPTN HomeFunction 204 can directly receive updated location information from aVisited Function in the MIPTN 202 if the subscriber is roaming withinthe MIPTN 202 or indirectly from a cellular Visited Function (e.g., VLR)if the MIPTN subscriber has roamed to the cellular network 260.

The MIPTN network 202 may include one or more subnetworks or areas, witheach subnetwork served by a corresponding MIPTN Visited Function (i.e.,the serving MIPTN Visited Function). An MIPTN Visited Function canreceive update location messages from a subscriber located in itssubnetwork or area requesting that the subscriber's location be updatedin the subscriber's Home Function. The MIPTN Visited Function thenprovides the updated subscriber location information (i.e., updatedlocation information describing where the subscriber can be reached) tothe subscriber's Home Function. The subscriber's Home Function may bethe MIPTN Home Function 204 for MIPTN subscribers or a cellular HomeFunction (e.g., HLR) for cellular subscribers.

According to an embodiment of the invention, cellular networksubscribers and MIPTN subscriber can access or communicate with a MIPTNVisited Function using one or more different access techniques such asvia radio or wireless or a cellular terminal, via an Integrated ServicesDigital Network (ISDN) terminal, via a personal computer over theInternet using the Internet Protocol (IP), etc. For example, referringto FIG. 2, Visited Function 206 is connected to a Base Station (BSS) 220via line 218 (e.g., through a GSM A interface or UMTS Iu interface).Thus, a mobile subscriber (MS) terminal 216 may communicate with theMIPTN Visited Function 206 using a radio or cellular access via BSS 220.Similarly, a MS terminal 212, which may be a personal computer (PC) oran ISDN terminal, may communicate with the MIPTN Visited Function 206via line 214 (which may be the Internet or an ISDN line, or othercommunication link). As a result, a subscriber can communicate orregister with a MIPTN Visited Function using different types ofsubscriber terminals. However, it is not necessary to allow differenttypes of subscriber terminals to communicate with the MIPTN VisitedFunction 206 so long as at least one type of terminal is accommodated(such as a MIPTN terminal or H.323 terminal, which may be provided as apersonal computer connected via the Internet to the MIPTN VisitedFunction). MIPTN terminal 230 may, for example, register with orcommunicate with MIPTN Visited Function 208.

The MIPTN 202 is coupled to the PSTN 240 via a standard IP-telephonyGateway 211. As described above in connection with FIG. 1, the standardIP-telephony Gateway 211 bridges the PSTN (a circuit switched network)to the MIPTN 202 (a packet-switched network). The standard IP telephonygateway 211 provides the appropriate translation or interworking betweentransmission formats (e.g., circuit-switched/packet-switched conversion,such as packetizing of the PSTN media to be sent over the MIPTN 202,unpacketizing the media) and between communication procedures (e.g.,signaling conversion). The standard IP-telephony Gateway 211 may performa static address translation between a directory number (e.g., MSISDN)and an IP address (e.g., the address of a Gatekeeper). It is a “static”address translation because the translation does not change when thesubscriber roams or changes locations. This static address translationperformed by standard IP-telephony Gateway 211, therefore, does notsupport mobility either within MIPTN 202 or between MIPTN 202 andcellular network 260.

According to an embodiment of the invention, the MIPTN 202 is alsocoupled to the PSTN 240 via one or more Gateway Functions, such asGateway Function 210. There are typically many Gateway Functions 210.According to an embodiment, the Gateway Function 210 bridges orinterfaces the PSTN 240 and the MIPTN 202. Alternatively GatewayFunction 210 interfaces directly between MIPTN 202 and the cellularnetwork 260, shown in FIG. 2 as Gateway Function 210A. Gateway Function210 will hereinafter refer to both possible locations of the GatewayFunction 210.

Gateway Function 210 provides the appropriate translation orinterworking between transmission formats and between communicationprocedures. However, as described in detail below, the Gateway Function210 also includes additional features or capabilities for mobilitysupport, including storing a dynamic correspondence or mapping between asubscriber identification and an address of a Visited Function (ineither the cellular network 260 or the MIPTN 202) where the subscriberhas roamed (or is located). This dynamic correspondence stored by theGateway Function 210 allows messages and calls to be successfullydelivered via Gateway Function 210 to cellular subscribers roaming tothe MIPTN 202, and to MIPTN subscribers roaming in the cellular network260.

According to an embodiment of the invention, the MIPTN 202 canaccommodate MIPTN subscribers roaming within the MIPTN 202. For example,a PSTN call to the MIPTN subscriber is routed to a Gateway, such as thestandard IP-telephony Gateway 211 (or to Gateway Function 210). TheGateway 211 then requests an IP address from the subscriber's MIPTN HomeFunction 204 where the subscriber can be reached. The Home Function 204returns the MIPTN network address (e.g., IP address) of the MIPTNVisited Function where the subscriber can be reached (e.g., where thesubscriber is registered). The Gateway 211 then delivers the receivedPSTN call to the MIPTN subscriber by setting up an IP-telephony calltowards the IP address of the serving MIPTN Visited Function. For a callreceived from another MIPTN subscriber (e.g., from MIPTN subscriberterminal 230), the Gateway 211 is not involved.

Cellular network 260 includes a gateway MSC (GW MSC) 262 and a HomeLocation Register (HLR) 264. The GW MSC 262 and HLR 264 may beconsidered to be a cellular network Home Function 266. The cellularnetwork 260 is divided into several location areas, with each locationarea being served by a corresponding serving MSC 272 and VisitingLocation Register (VLR) 270. Thus, the serving VLR 270 and the servingMSC may be considered to be a cellular network Visited Function 274.Only one pair of serving MSC and VLR are shown in FIG. 2.

The Gateway Function 210 and MIPTN 202 accommodate subscriberregistration and call delivery for cellular subscribers which haveroamed to the MIPTN 202 and for MIPTN subscribers which have roamed tothe cellular network 260. In both cases call delivery involves queryingthe subscriber's Home Function (i.e., the HLR 264 for cellularsubscribers and the MIPTN Home Function 204 for MIPTN subscribers) forupdated location information for the subscriber stored during aregistration process. The call is then forwarded via the GatewayFunction 210 to the Visited Function of the network where the subscriberhas roamed based on the updated location information. The call ormessage delivery for internetwork roaming will usually include theGateway Function 210 using a dynamic mapping or correspondence storedduring registration to identify an address of the serving VisitedFunction where the subscriber is located.

According to an embodiment of the present invention, each MIPTNsubscriber or cellular network subscriber is identified by one or moreunique identifiers or aliases. The aliases can take many forms, so longas it globally and uniquely identifies the user.

According to an embodiment of the invention, it is assumed that everymobile subscriber has been assigned at least one E.164 number, calledthe Mobile Subscriber ISDN number (MSISDN) in E.164 format (or othercellular/PSTN format) as the directory number for calling thesubscriber. The MSISDN logically points to the subscriber's HomeFunction. According to an embodiment of the invention, each subscriberwill also be identified by an International Mobile Subscriber Identity(IMSI). Both the MSISDN and IMSI logically point towards thesubscriber's Home Function (either the MIPTN Home Function 204 for MIPTNsubscribers or the cellular Home Function 266 for cellular subscribers).

With respect to the network that is not the subscriber's Home network,the subscriber's MSISDN and IMSI (or other subscriber identification)actually will point to the domain boundary (i.e., the boundary betweenthe cellular network 260 and MIPTN 202). For example, for a MIPTNsubscriber roaming in the cellular network 260, the routing tables inthe cellular/PSTN networks will route a registration message from theMIPTN subscriber based on the subscriber's IMSI, hop-by-hop, from thecellular Visited Function until the registration message reaches one ofthe Gateway Functions 210. Thus, in the cellular network 260 or PSTN240, a MSISDN or IMSI for a MIPTN subscriber will point to one of theGateway Functions 210. Similarly, in the MIPTN 202, a MSISDN or IMSI fora cellular subscriber will point to one of the Gateway Functions 210.

In addition, as well understood by those skilled in the art, in the PSTN240 and Cellular network 260 typically use common channel signalingbased on the Signaling System 7 (SS7) protocol for network signaling(e.g., Call setup, etc.). SS7 is actually a set of protocols, includingSignaling Connection Control Part (SCCP). SCCP is responsible foraddressing and routing of messages in general. SCCP provides a function,called Global Title Translation (GTT), which is used to find a realaddress of a node based on some Global Title. Examples of a Global Titleinclude a MSISDN (e.g., or other E.164 number) and an IMSI. However, IPaddresses cannot be used to route messages or calls in the PSTN 240 orcellular network 260.

In contrast, message or datagram routing in IP networks or the MIPTN 202is performed based on the transport address (e.g., including an IPaddress and a port number). PSTN and cellular addresses (e.g., E.164numbers, IMSI identifiers and MSISDN numbers) are not typicallyrecognized in IP networks.

As a result, when a subscriber roams between the MIPTN 202 and thecellular network 260, the subscriber's Home Function and the servingVisited Function are in different domains (i.e., different types ofnetworks) and use different types of addresses to identify thesubscriber's location. For example, when a cellular subscriber (i.e.,having a Home Function 266 in cellular network 260) roams to a MIPTNVisited Function 208 in the MIPTN 202, the serving MIPTN VisitedFunction 208 generates and provides the subscriber's updated location asan IP address, which will not be recognized in the subscriber's cellularHome Function 266 (i.e., cannot be used in HLR 264 to indicatesubscriber's location). Likewise, when a MIPTN subscriber roams to thecellular network 260, the serving cellular Visited Function 274 providesupdated location information compatible with the PSTN/cellular addresses(e.g., E.164 format), but which is incompatible with the IP addressesused by the subscriber's MIPTN Home Function 204. Therefore, the GatewayFunction 210 must perform a function of address translation between thePSTN/cellular addresses and the MIPTN or IP addresses.

The Gateway Function 210 looks like either a MIPTN Home Function 204 ora MIPTN Visited Function towards the MIPTN 202. For example, the GatewayFunction 210 appears to be a MIPTN Home Function to the MIPTN VisitedFunction 206 when updated location information is sent from the MIPTNVisited Function 206 towards the subscriber's HLR 264. The GatewayFunction 210 appears to be a MIPTN Visited Function 206 to the MIPTNHome Function 204 when the Home Function 204 receives updated locationinformation from a serving cellular Visited Function 274. In a similarmanner, the Gateway Function 210 looks like either a cellular HomeFunction 266 (e.g., HLR 264) or a cellular Visited Function 274 to thecellular network 260.

The MIPTN Home Function

FIG. 3 is a block functional diagram illustrating a Mobile IP-telephonynetwork Home Function according to an example embodiment of the presentinvention. The MIPTN Home Function 204 includes a Call ProcessingService (CPS) 410, a Location and Directory Service (LDS) 412 and a HomeFunction Database (HDB) 414.

HDB 414 stores subscriber profiles and location information for MIPTNsubscribers (e.g., the IP address and port number of the VisitedFunction identifying where the subscriber can be reached). The LDS 412interfaces other entities to the HDB 414 by performing informationstorage and retrieval to HDB 414 upon request. The HDB also maintainsthe mapping or correspondence between IMSI, MSISDN and the transportaddress of the serving Visited Function where the subscriber can bereached. The transport address identifying where the subscriber can bereached will typically be the transport address of the serving MIPTNVisited Function if the MIPTN subscriber is roaming within the MIPTN202, and will be the IP address of the Gateway Function if the MIPTNsubscriber has roamed to the cellular network 260 (the serving cellularVisited Function can be accessed through the Gateway Function 210). TheIMSI and MSISDN for a subscriber are static, whereas the servingtransport address is dynamic (i.e., may change from time to time as thesubscriber changes locations). Subscriber information (including updatedsubscriber location information provided to LDS 412 for storage in HDB414) is provided via line 422.

The CPS 410 receives signaling for incoming calls and forwards thesignaling to the appropriate Visited Function (or to the GatewayFunction if directed to the cellular network 260). CPS 410 requests thetransport address corresponding to an identified called subscriber(based on IMSI or MSISDN) from the LDS 412. LDS 412 provides therequested transport address to the CPS 410. The CPS then forwards thesignaling to the call control entity (CCE) of the Visited Function orGateway Function 410. Before allowing the call to be routed orestablished, the CPS 410 may also issue a status enquiry to the MIPTNVisited Function (or to the Gateway Function where the MIPTN subscriberhas roamed to the cellular network) to ensure that the called subscriberis available to receive the call. IP-telephony signaling is providedover line 426 and may be, for example, H.323/Q.931 type signaling.

A MIPTN Short Message Service Center 420 is connected to the MIPTN HomeFunction 204 via line 432. The MIPTN Short Message Service Center (SMSC)420 is somewhat similar to the SMSC provided in GSM, but SMSC 420provides mobility support. SMSC 420 stores and forwards Short MessageService (SMS) messages to mobile subscribers (either MIPTN or cellularsubscribers) located within the MIPTN network 202 or located in thecellular network 260, including subscribers that are roaming between theMIPTN 202 and the cellular network 260.

The MIPTN Visited Function

FIG. 4 is a functional block diagram illustrating a Mobile IP-telephonynetwork Visited Function according to an example embodiment of thepresent invention. The MIPTN Visited Function 208 includes a CallControl Entity for the Visited Function (CCEVF) 510 for controllingoperation of the Visited Function, a Visited Function Database (VDB) 512for storing subscriber information, and an Access Gateway (AGW) 520 forinterfacing between the IP-telephony network (MIPTN 202) and thesubscriber terminal (if not an IP-telephony terminal). As shown in FIG.4, signals on the left or MIPTN side 508 are connected to the MIPTN 202,and signals on the right or subscriber terminal side 507 are connectedto the subscriber terminals.

The AGW 520 is optional and includes a Signaling Gateway (SG) 522 and aMedia Gateway (MG) 524. AGW 520 allows a subscriber terminal other thanan IP-telephony terminal to register with or communicate with the MIPTNVisited Function 208. Examples include a radio or cellular subscriberterminal connected via line 538, an ISDN terminal connected via line539, etc. If the subscriber terminal is an IP-telephony terminal, no AGW520 is necessary because the media and signaling used by theIP-telephony subscriber terminal are compatible with the MIPTN VisitedFunction 208 (e.g., the Internet Protocol).

SG 522 provides an interworking function to translate or convert betweenIP-telephony signaling (e.g., H.323 signaling) for calls and SMS messagesignaling received from CCEVF 510 via line 542 and the type of signalingused by the subscriber terminal connected via lines 538 or 539.Similarly, MG 524 provides an interworking function to translate orconvert between the IP-telephony media (e.g., packetized data, voice,video) received over line 536 and the SMS messages received over line544 and the media type used by the subscriber terminal connected vialines 538 and 539. An example of an IP-telephony protocol fortransporting media over IP is Real-time Transport Protocol (RTP), usedon line 536.

The CCEVF 510 controls the overall operation of the Visited Function206, including handling or controlling the subscriber registrationprocess. At the beginning of the subscriber registration, the CCEVF 510receives an update location message via line 530 from a subscriber whichis registering with the Visited Function 208. In essence, the updatelocation message from the subscriber is a request to the VisitedFunction to update the subscriber's location information maintained inthe subscriber's Home Function (either the MIPTN Home Function or thecellular Home Function). The CCEVF 510 then issues the appropriateupdate location message to the subscriber's Home Function to provide thetransport address (IP address) of the Visited Function 208 where thesubscriber can be reached. The CCEVF 510 also receives and storessubscriber information (e.g., the subscriber's profile received from thesubscriber's Home Function). The subscriber information is stored in theVDB 512. The CCEVF 510 also receives status enquiries from the HomeFunction 204. The CCEVF 510 receives SMS messages and signaling overline 534. The CCEVF 510 forwards the received messages via line 544 toMG 520 for translation and delivery to the subscriber. CCEVF 510receives and stores subscriber profile from a Home Function duringregistration.

The MIPTN Visited Function manages micro-mobility of the subscriberterminal if the subscriber terminal is separate from the VisitedFunction. For example, in the case where the MIPTN Visited Functioncontrols several location areas in MIPTN 202, the MIPTN Visited Functionmaintains in VDB 512 a dynamic mapping between each subscriber's IMSIand the location area in MIPTN 202 where the subscriber is located.Thus, while the subscriber terminal may roam within several locationareas which are controlled by a single MIPTN Visited Function, thesubscriber's Home Function 204 stores a single IP address at which thesubscriber can be reached (i.e., the IP address of the serving MIPTNVisited Function). The Home Function 204 is not informed every time thesubscriber terminal changes location areas, but rather, only when thesubscriber roams to a location area controlled by a different VisitedFunction (i.e., having a different IP address).

There is at least one transport address (IP address and port number)corresponding to each MIPTN Visited Function. If only one address isused for a Visited Function 208, the address may be referred to as theVF_TA (for Visited Function transport address). However, according to anembodiment of the invention, different transport addresses correspondingto the Visited Function 208 may be used for different purposes. Forexample a CCEVF_TA transport address may be used for IP-telephony callsignaling, an RTP_TA address may be used for IP-telephony media, and aSMS_TA may be used for SMS messages and signaling. Each of theseaddresses may be a different IP address, or may have the same IP addressand a different port number (e.g., a different default port number maybe used for each).

The Gateway Function 210

FIG. 5 is a functional block diagram illustrating a Mobile IP-telephonynetwork Gateway Function according to an example embodiment of thepresent invention. Signals on the left or PSTN side 606 of GatewayFunction 210 are connected to the PSTN 240 or cellular network 260,while signals on the right or IP-telephony side 608 are connected to theMIPTN 202. Gateway Function 210 includes a Trunking Gateway (TGW) 610, aCall Control Entity for the Gateway Function (CCEGW) 620, a SMS Gateway630 and a Gateway Database (GWDB) 634.

TGW 610 interfaces the PSTN network 240 and the MIPTN 202, and includesa Signaling Gateway (SG) 612 and a Media Gateway 614. MG 614 providesthe translation or interworking between the IP-telephony media stream(e.g., H.323 RTP streams) on line 644 and the PSTN Time DivisionMultiplexed (TDM) media stream on line 642. Likewise, SG provides atranslation or interworking between the PSTN/cellular signaling (such asMobile Application Part or MAP, and ISDN User Service Part or ISUP)provided on line 640 and the SMS signaling (received on line 650 andprovided to SG 612 on line 660) and IP-telephony call signaling (such asH.323/Q.931 signaling received on line 648 and provided to SG 612 online 662).

The CCEGW 620 controls overall operation of Gateway Function 620. TheCCEGW 620 maintains a dynamic mapping or correspondence between the IMSIfor each subscriber and the address of the Visited Function where thesubscriber is located or registered (where the subscriber can bereached) where internetwork roaming is involved (i.e., where subscribersare roaming between cellular network 260 and MIPTN 202). This dynamicmapping information is obtained by the CCEGW 210 and stored in the GWDB634 during a subscriber registration process (which must occur through aGateway Function 210 for internetwork roaming). SMSGW 630 can accessthese dynamic mappings stored in GWDB 634 for the delivery of SMSmessages and signaling received over line 650.

Static and Dynamic Address Translations

Some of the functionality of Gateway Function 210 and of the standardIP-telephony gateway 211 will be explained, with respect to addressmappings or translations. First, for subscriber registrations, the MIPTNVisited Function and the standard IP-telephony gateway 211 can use alookup table or a distributed technique (such as a Global TitleTranslation or a remote database) to statically translate the subscriberidentification (typically, an IMSI, but not necessarily an E.164 number)to a Home Function IP address. If the visiting subscriber is roamingfrom the cellular network 260, the IP address actually leads to one ofthe Gateway Functions 210. (See, for example, static translation byVisited Function of IMSI to IP address of Gateway Function 210, steps1-2, FIG. 8). This is a “static” translation because the IP addresscorresponding to the IMSI does not change when the subscriber changeslocations or roams.

Secondly, during a first leg of call delivery (towards a Home Function),a calling entity or a standard IP-telephony gateway 211 also staticallytranslates between the called subscriber identification (such as aMSISDN or IMSI) to an IP address of the subscriber's Home Function.(See, for example, static translation performed by standard Gateway 211from MSISDN to Home Function IP address, steps 1-2, FIG. 10). This isalso a static translation.

Finally, for call delivery on a roaming leg of the call from a MIPTNHome Function 204 to a cellular Visited Function or from a cellular HomeFunction 266 to a MIPTN Visited Function, the Gateway Function 210 mustmake an address translation based upon dynamic mappings between asubscriber identification and a Visited Function address establishedduring the subscriber registration process. This dynamic mapping is atemporary correspondence between an IMSI (or other subscriberidentification) and a cellular/PSTN address (such as a VLR number inE.164 format) or a temporary correspondence between an IMSI and an IPaddress (such as the IP address of a Visited Function). (See, forexample, address translation performed by Gateway Function 210 basedupon dynamic mapping between IMSI and VLR number of cellular VisitedFunction, steps 2-3, FIG. 11). The Gateway Functions 210 of the presentinvention store these dynamic address mappings during registration tosupport internetwork roaming and message and call delivery. Thesedynamic mappings are not performed or used in standard IP-telephonyGateways 211, and thus, standard Gateway 211 does not support mobilitybetween the cellular and MIPTN networks.

Subscriber Registration

Subscriber registration is used to constantly maintain updated statusand location information in the subscriber's Home Function, and shouldbe performed each time the subscriber changes locations. The subscriberterminal may monitor one or more predetermined channels for broadcastinformation identifying the MIPTN subnetwork or the cellular subnetworkor location area. Based on this information, the subscriber or thesubscriber terminal can determine whether the subscriber has changedlocations (e.g., by comparing subscriber's current location to previouslocation), requiring a registration with the new Visited Function.Alternatively, a Visited Function may detect the presence of a newsubscriber terminal in its area(s) of control, thus requiring subscriberregistration. The registration with the new serving Visited Functionprovides updated subscriber location and status information to thesubscriber's Home Function. The subscriber's updated status and locationinformation stored in the subscriber's Home Function can then be used todeliver calls and messages to the called subscriber, regardless of thesubscriber's location.

The subscriber status can include, for example, whether the subscriberterminal is connected or not connected to a network. A subscriber canalso select other status options, such as blocking all incoming calls,while allowing the subscriber to place outgoing IP telephony calls. If acall is received that is intended for a subscriber that is either notconnected to the network or has blocked all incoming calls, thereceiving Gateway Function 210 (after obtaining the called subscriber'sstatus and location from the called subscriber's Home Function), caneither decline to place the requested call (e.g., return a busy orunavailable indication to the caller because the called party is notconnected or incoming calls are blocked) or route the call to apredetermined IP address associated with the subscriber, such as thesubscriber's answering machine or voice mail system.

FIG. 6 is a diagram illustrating an example subscriber registration fora Mobile IP-Telephony subscriber roaming within the Mobile IP-TelephonyNetwork. In the registration process illustrated in FIG. 6, it isassumed that the MIPTN subscriber has roamed to a new location area orsubnetwork within MIPTN 202. At step 1, the MIPTN subscriber terminal(MS in FIG. 6, meaning mobile subscriber) sends an update locationmessage to the serving MIPTN Visited Function, providing thesubscriber's IMSI. As noted above, the subscriber terminal can accessthe MIPTN Visited Function using a variety of different accesstechniques (e.g., IP-telephony, ISDN, radio or cellular).

Because the IMSI points to the Home Function 204, the MIPTN VisitedFunction statically translates the IMSI to the IP address of the HomeFunction 204. For example, the Visited Function can use a database orlook-up table or other technique to statically translate thesubscriber's IMSI to the transport address of the subscriber's HomeFunction 204. In addition (or in the alternative), a distributedtechnique, such as Global Title Translation can be used to identify theactual IP address of the Home Function 204 based on the subscriber'sIMSI.

At step 2 of FIG. 6, the MIPTN Visited Function sends an update locationmessage (e.g., packet or datagram) to the subscriber's MIPTN HomeFunction 204 and provides the transport address of the Visited Function(VF_TA) and the status of the subscriber. The VF_TA is the IP address atwhich the subscriber can be reached in the MIPTN 202. The HDB 414 (FIG.3) receives and stores the updated location information (e.g., VF_TA)and status information for the subscriber. Where different addresses areused at the Visited Function, the Visited Function may provide theCCEVF_TA.

At step 3 of FIG. 6, the Home Function 204 sends an insert subscriberdata message to the serving Visited Function (using the VF_TA address asthe destination address) to provide the subscriber's complete profile(or portion thereof) to the serving Visited Function. The VDB 512 (FIG.4) receives and stores the subscriber profile. At step 4 of FIG. 6, theHome Function 204 retrieves the transport address which previouslyindicated the location of the subscriber (the address of the old VisitedFunction). The Home Function 204 then sends a message to cancel thelocation information and subscriber profile stored at the old VisitedFunction for the subscriber (e.g., providing the IMSI) because thesubscriber is no longer located at the old Visited Function.

FIG. 7 is a diagram illustrating an example subscriber registration fora Mobile IP-Telephony subscriber roaming to a cellular network. In FIG.7, it is assumed that a MIPTN subscriber (i.e., having a Home Function204 in the MIPTN 202) has roamed to a cellular network 260. At step 1 ofFIG. 7, the subscriber terminal (MS) sends an update location message tothe serving MSC 272/VLR 270 in the serving cellular Visited Function 274in cellular network 260, and provides the subscriber's IMSI. Step 1 isperformed as a cellular procedure.

At step 2 of FIG. 7, the serving VLR 270 sends an update locationmessage as a cellular procedure to the subscriber's Home Function basedon the subscriber's IMSI, providing the VLR number in E.164 format (asthe subscriber's location in the cellular network 260). The servingMSC/VLR is not aware that the subscriber is a MIPTN subscriber. In thiscase, the subscriber's Home Function is located in the MIPTN 202 and thesubscriber's IMSI, therefore, points to one of the Gateway Functions210.

At step 3 of FIG. 7, the Gateway Function 210 receives the updatelocation message as a cellular procedure or message, including thesubscriber's IMSI and the VLR number in E.164 format. The GatewayFunction 210 stores the dynamic correspondence between the IMSI and theVLR number in a table. The Gateway Function 210 then translates theupdate location message from a cellular procedure to a MIPTN procedureor update location message, which is sent along with the IP address ofthe Gateway Function 210 (GW_TA) to the subscriber's Home Function 210.Gateway Function 210 can obtain the IP address of the Home Function 204from the subscriber's IMSI because, in MIPTN 202, a MIPTN subscriber'sIMSI points to the MIPTN Home Function 204. Alternatively, the GatewayFunction 210 can use a distributed technique such as or similar toGlobal Title Translation to obtain the IP address of the MIPTN HomeFunction 204.

At step 4 of FIG. 7, the MIPTN Home Function 204 receives the updatelocation message, including the subscriber's IMSI and the IP address ofthe Gateway Function 210. The Home Function 204 stores the IP address ofthe Gateway Function (GW_TA) as the location of the subscriber. GatewayFunction 210 then issues an insert subscriber data message back to theGateway Function 210 at step 4, including the subscriber's profile ordata (s. Data) and the subscriber's IMSI.

At step 5 of FIG. 7, the Gateway Function 210 receives the insertsubscriber data message, and identifies the VLR number corresponding tothe IMSI. Gateway Function 210 then sends an insert subscriber datamessage as a cellular/PSTN procedure to the VLR number (the servingVLR). The serving VLR then stores the subscriber profile correspondingto the IMSI.

Although not shown in FIG. 7, the MIPTN Home Function could also send amessage to the old Visited Function to cancel the previous location andprofile. If the old Visited Function is a MIPTN Visited Function, theMIPTN Home Function 204 can send this cancel message directly to the oldMIPTN Visited Function. However, if the old Visited Function is actuallya cellular Visited Function 274 (in the cellular network 260), thecancel message must be sent through the Gateway Function 210, whichforwards a cancel message to the appropriate VLR number (in E.164format) previously stored in the Gateway Function 210 as correspondingto the same IMSI.

FIG. 8 is a diagram illustrating an example subscriber registration fora cellular network subscriber roaming to a Mobile IP-Telephony network.In FIG. 8, it is assumed that a cellular subscriber has roamed to aMIPTN 202. At step 1 of FIG. 8, the cellular subscriber (MS) sends anupdate location message to the serving MIPTN Visited Function, includingthe subscriber's IMSI. As described above, the subscriber terminal canaccess or register with the MIPTN Visited Function using a variety ofdifferent access techniques (IP-telephony terminal, radio terminal, ISDNterminal etc.). Thus, the MIPTN Visited Function may translate thesignaling and data received from the subscriber terminal to IP-telephonyformat (see FIG. 4) if not already in IP-telephony format.

At step 2 of FIG. 8, the MIPTN Visited Function sends an update locationmessage to the IP address of the Home Function of the subscriber. Inthis case, the cellular subscriber's IMSI in the MIPTN 202 points to oneof the Gateway Functions 210. The MIPTN Visited Function thereforestatically translates the IMSI to an IP address that leads to one of theGateway Functions 210. Thus, the MIPTN Visited Function sends the updatelocation message to the Gateway Function 210. The message includes thesubscriber's IMSI and the IP address of the MIPTN Visited Function(VFTA). The CCEVF_TA address can be sent if different transportaddresses are used for the MIPTN Visited Function.

At step 3 of FIG. 8, the Gateway Function 210 receives the updatelocation message as a MIPTN message, including subscriber's IMSI and thesubscriber's location (i.e., the VF_TA). The Gateway Function 210 storesthe dynamic correspondence of the IMSI and the VF_TA in a table. TheIMSI points to the cellular Home Function 266 of the subscriber (incellular network 260). Then, the Gateway Function 210 sends an updatelocation message as a cellular/PSTN procedure or message to thesubscriber's HLR 264 in the cellular Home Function 266. This updatelocation message includes the subscriber's IMSI and the Gateway Functionnumber of Gateway Function 210 provided as a E.164 number or in anotherPSTN/cellular format. In other words, the Gateway Function number isprovided as a pseudo-VLR number to the HLR, to identify the “VLR” atwhich the subscriber has registered. But in this case, the VLR number isa pseudo-VLR number because the number actually identifies the GatewayFunction 210 through which the subscriber can be reached (i.e., theGateway Function number in E.164 format appears to be a VLR number tothe HLR). The subscriber's HLR 264 (FIGS. 1 and 2) then stores theupdated status and location information (i.e., the Gateway number) forthe IMSI.

At step 4 of FIG. 8, the HLR 264 sends an insert subscriber data messageas a cellular/PSTN procedure or message to the Gateway Function 210(based on the Gateway Function number provided in E.164 format),providing the subscriber's IMSI and the subscriber's profile (s. data)maintained in the HLR 264.

At step 5 of FIG. 8, the Gateway Function 210 receives the insertsubscriber data message from the HLR. The Gateway Function 210identifies the IP address corresponding to the IMSI stored earlier(i.e., the VF_TA). The Gateway Function 210 then sends an insertsubscriber data message as a MIPTN procedure or message to the servingMIPTN Visited Function, providing the subscriber' IMSI and thesubscriber data or profile to the serving Visited Function. The VDB 512(512) in the MIPTN Visited Function 208 then stores the subscriber dataor profile corresponding to the IMSI.

Although not shown in FIG. 8, the HLR may also send a cancel location(or cancel profile) message to the old serving Visited Function. If thesubscriber was previously registered with another serving MIPTN VisitedFunction, the old VLR number would identify the Gateway Function 210,and the Gateway Function would send a cancel location message to the oldserving MIPTN Visited Function (based on a previously stored dynamic IPaddress or VF_TA for this same IMSI).

Some Alternative Embodiments for Visited Functions and SubscriberTerminals

According to an embodiment of the invention, the subscriber terminal andthe MIPTN Visited Function are separate and distinct entities (e.g., seeFIG. 2). In such case, the subscriber terminal contacts the VisitedFunction to perform registration, and the Visited Function communicateswith the other entities to provide updated location information to thesubscriber's Home Function. In such case, one Visited Function canaccommodate multiple subscribers. Where multiple subscribers areconnected to one Visited Function, there may be one IP address for allsubscribers, or different IP addresses assigned to each subscriber (buteach IP address still pointing to the Visited Function). In the eventthat one IP address is used for all (or multiple) subscriber terminalsconnected to the Visited Function, there must be a way for the VisitedFunction to distinguish between messages directed to each subscriberterminal. Thus, a different port number can be assigned to eachsubscriber, or the IMSI for each subscriber can be provided within eachmessage to identify the intended recipient (subscriber).

However, according to an alternative embodiment of the invention, theMIPTN Visited Function can be provided as part of the subscriberterminal (e.g., the Visited Function may be one or more softwareroutines running on the subscriber terminal). In this embodiment, it isa Visited Function software routine in the subscriber terminal thatcontacts the subscribers' Home Function (either directly or through theGateway Function 210) to update the subscriber's location informationmaintained at the Home Function. The subscriber terminal would alsodirectly receive other messages sent to the Visited Function that areintended for the subscriber. In the case that the Visited Function isprovided as a part of the subscriber terminal, the IP address of theVisited Function may also be the address of the subscriber terminal.

Call Delivery Examples

FIG. 9 is a diagram illustrating an example call delivery of anIP-telephony call to a Mobile IP-telephony subscriber roaming in theMobile P-telephony network. In FIG. 9, it is assumed that a MIPTNsubscriber has contacted a MIPTN Visited Function to performregistration (e.g., see FIG. 6 for the registration process). At step 1of FIG. 9, the calling entity sends a call setup/address request messageto the MIPTN Home Function 204, and provides the MSISDN of the calledsubscriber. The MIPTN Home Function stores a static table identifyingthe correspondence between IMSI and MSISDN for each subscriber. TheMIPTN Home Function 204 translates the MSISDN to the corresponding IMSIfor the subscriber.

In some cases it may be necessary for the Home Function 204 to determineif the subscriber terminal is presently available to receive therequested call. An example is where the subscriber terminal is acellular terminal connected to a Visited Function, and the Home Functionmust ensure that the subscriber terminal has not temporarily passedunder a building or bridge, lost power, etc. Such a status enquiry maynot be necessary for some types of subscriber terminals, which are notsubject to interference, etc. (such as an ISDN terminal or IP-telephonyterminal).

Steps 2-3 in FIG. 9 are performed to check the status of the subscriberterminal. In step 2, the Home Function sends a status enquiry message tothe serving MIPTN Visited Function where the subscriber terminal isregistered. The IP address of the serving Visited Function was obtainedand stored by the Home Function 204 during registration. In the casewhere the subscriber terminal is separate from the Visited Function, theVisited Function queries the subscriber terminal to obtain theterminal's status (steps 3 a and 3 b). The Visited Function thenforwards the status of the terminal (e.g., able to receive a call, orunable to receive a call) back to the Home Function 204, step 3 of FIG.9.

At step 4 of FIG. 9, if the terminal is able to receive the call, theHome Function 204 returns an address response message to the callingentity, providing the address (e.g., VF_TA or CCEVF_TA) of the VisitedFunction where the IP-telephony call should be forwarded. If thesubscriber terminal is unavailable, the returned address responsemessage may indicate the subscriber terminal is unavailable and returnan IP address of a voice mail box, etc.

At step 5 of FIG. 9, the calling entity sets up or establishes anIP-telephony call from the calling entity towards the IP address of theMIPTN Visited Function (including call signaling for call setup and thenproviding the call media or voice). The subscriber's IMSI may beprovided as an alias if needed to identify the called subscriber. Callsignaling could be sent to the Visited Function at the CCEVF_TA address,while the Visited Function address for sending the RTP media (RTP_TA)could be negotiated separately by the Visited Function and callingentity.

At step 6 of FIG. 9, if the subscriber terminal is separate from theVisited Function, the Visited Function would then forward the call overthe medium or interface used by the subscriber terminal (e.g., ISDN,wireless or cellular). If the subscriber terminal is connected to theVisited Function via IP-telephony, the IP-telephony call could just beforwarded from the Visited Function to the address of the subscriberterminal (or set up directly to the subscriber terminal). In the eventthat the Visited Function is provided as a part of the subscriberterminal, step 6 is unnecessary.

The are two ways in which an IP-telephony call may be setup ornegotiated. One way (which is illustrated in FIG. 9) is where callcontrol signaling is routed directly between the calling entity and theVisited Function. A second way is to route all call control signalingbetween the calling entity and the Visited Function through the HomeFunction. This second technique allows the Home Function 204 to keeptrack of the identification of the call parties, when the call wasstarted and ended, etc., which can be used for billing or otheradministrative processes. In this technique (where signaling is routedthrough the Home Function, the calling entity need not receive theVF_TA. During call setup, the parties could negotiate the VisitedFunction address for transporting the IP-telephony call media (RTP_TA)if separate signaling and media addresses are used at the VisitedFunction. Regardless whether the call control signaling is sent throughthe Home Function, the IP-telephony call media (i.e., packetized voice)should be sent directly between the two parties (the IP-telephony mediais not routed through the MIPTN Home Function).

FIG. 10 is a diagram illustrating an example delivery of a PSTN call toa Mobile IP-telephony subscriber roaming in the Mobile IP-telephonynetwork. It is assumed in FIG. 10 that the MIPTN subscriber has alreadycontacted a MIPTN Visited Function to perform registration. The calldelivery of a PSTN call to a MIPTN subscriber roaming in the MIPTN 202is similar to the call delivery of a MIPTN call (shown in FIG. 9). It isnot necessary to use Gateway Function 210 here (Gateway 211 willsuffice) because this is not internetwork roaming (rather, FIG. 10involves roaming within MIPTN 202).

At step 1 of FIG. 10, a PSTN call is directed to a standard IP-telephonyGateway 211 based on the called subscriber's MSISDN. The standardIP-telephony Gateway 211 performs a static translation between eachsubscriber's MSISDN and the transport address of the subscriber's HomeFunction 204, HF_TA (e.g., IP address and port number of Home Function204). The standard IP-telephony Gateway 211 sends a call setup/addressrequest message to the MIPTN Home Function 204, providing the calledsubscriber's MSISDN. The MIPTN Home Function 204 stores a staticcorrespondence between each subscriber's IMSI and MSISDN, and stores adynamic correspondence between the subscriber's IMSI and thesubscriber's updated location (the latter obtained during registration).In this case, the subscriber's location is the IP address (e.g., VF_TA)of the Visited Function where the subscriber terminal is registered.After obtaining the subscriber's status (if necessary) at steps 3-4 ofFIG. 10, the MIPTN Home Function 204 may then send an address responsemessage at step 5, providing the address of the MIPTN Visited Functionwhere the subscriber is registered and can be reached (e.g., the VF_TAwhere one address used and the CCEVF_TA where separate signaling andmedia addresses are used). As in FIG. 9, the signaling may be eitherrouted directly between the standard IP-telephony Gateway 211 and theMIPTN Visited Function, or through the MIPTN Home Function 204. Notealso that in the response messages (i.e., messages of steps3 b, 4 and 5of FIG. 10) in the Figures, it is not always necessary to provide theIMSI because identifiers are typically used to correlate a response to aparticular request (thus, the IMSI being implicitly provided).

At step 6 of FIG. 10, an IP-telephony call is set up from the GatewayFunction towards the address of the MIPTN Visited Function (with themedia sent to either VF_TA or RTP_TA address of the MIPTN VisitedFunction). As noted above, the IP-telephony call may use the IMSI as analias if needed by the Visited Function to distinguish between multiplesubscriber terminals. If the subscriber terminal and MIPTN VisitedFunction are separate, the MIPTN Visited Function then forwards thereceived call to the subscriber terminal over the medium used by thesubscriber terminal, step 7.

FIG. 11 is a diagram illustrating an example delivery of an IP-telephonycall to a Mobile IP-telephony subscriber roaming to a cellular network.FIG. 12 is a block diagram illustrating an example delivery of anIP-telephony call to a Mobile IP-telephony subscriber roaming to acellular network, corresponding to FIG. 11. In FIGS. 11 and 12, it isassumed that the MIPTN subscriber has already contacted a servingcellular Visited Function 274 (e.g., serving VLR 270, FIG. 2) toregister as described in FIG. 7. As part of the registration process forthe MIPTN subscriber that has roamed to the cellular network 260, theGateway Function 210 has stored a dynamic correspondence between thesubscriber's IMSI and the VLR number (e.g., in E.164 format) thatidentifies the serving VLR in the cellular network where the subscriberis located (where subscriber has registered), as described withreference to FIG. 7. As always, the subscriber's Home Function 204 hasstored the transport address where the subscriber can be reached. Inthis case, because the subscriber has roamed to the cellular network260, the subscriber's location information in the Home Function 204identifies the IP address of the Gateway Function 210 (i.e., the GW_TA).

At step 1 of FIG. 11, the calling entity sends a call setup/addressrequest message to the subscriber's Home Function based on the MSISDN,providing the called subscriber's MSISDN. This step is an example of thesignaling provided on signaling leg A in FIG. 12. (As noted above, inthe MIPTN 202, the MIPTN subscriber's MSISDN points toward thesubscriber's MIPTN Home Function 204).

The Home Function 204 stores a static correspondence between thesubscriber's MSISDN and IMSI. The Home Function identifies the IMSIcorresponding to the MSISDN, and then sends a status enquiry message tothe Gateway Function using the stored GW_TA corresponding to the calledsubscriber's IMSI (from the dynamic mapping), providing the IMSI, step2. This step is an example of the signaling provided at leg B on FIG.12.

The Gateway Function 210 receives the status enquiry message (includingthe called subscriber's IMSI), and identifies the VLR number(identifying the serving VLR or cellular Visited Function where thesubscriber has registered) corresponding to the subscriber IMSI (usingthe dynamic mapping obtained during registration). At step 3 of FIG. 11,the Gateway Function 210 sends a Route Number (RN) request message as acellular procedure or message (including the called subscriber's IMSI)to the identified VLR number (i.e., to the cellular Visited Functionwhere the called subscriber has registered). The message of step 3 is anexample of the signaling provided on signaling leg C of FIG. 12.

The cellular Visited Function 274 then determines the status of thecalled subscriber. If the called subscriber is reachable or able toreceive the call, the cellular Visited Function 274 assigns a roamingnumber (RN) to the subscriber. At step 4 of FIG. 11, the cellularVisited Function 274 then sends a RN response message back to theGateway Function, including the roaming number assigned to the calledsubscriber (if the subscriber is reachable). Step 4 of FIG. 11 isanother example of the signaling provided on leg C of FIG. 12. (Althoughthe arrows on FIG. 12 are shown in one direction to show an initialdirection, it should be understood that one or more of the legs in FIG.12 provide bidirectional signals for each leg). If the subscriber isunreachable or unable to receive the call, no RN is assigned or returnedto the Gateway Function 210.

The Gateway Function 210 receives the RN response message, and storesthe dynamic correspondence between the subscriber's IMSI and the RoamingNumber (RN) assigned to the subscriber. At step 5 of FIG. 11, theGateway Function 210 sends a status response message to the MIPTN HomeFunction 204, providing the status of the called subscriber. The messageof step 5 is another example of the signaling provided on leg B of FIG.12.

At step 6 of FIG. 11, the MIPTN Home Function 204 sends an addressresponse back to the calling entity, providing the transport address(GW_TA) of the Gateway Function 210, where the called subscriber can bereached in the MIPTN 202. The message of Step 6 of FIG. 11 is anotherexample of the signaling provided on leg A of FIG. 12.

At step 7 of FIG. 11, the calling entity sets up or establishes anIP-telephony call towards the address (GW_TA) of the Gateway Function210, and may provide the called subscriber's IMSI as an alias ifnecessary (or a unique transport address assigned to the subscriber forthe GW_TA could be used instead). The IP-telephony call of step 7 ifFIG. 11 corresponds to media leg D of FIG. 12.

The Gateway Function 210 receives the IP-telephony call, and thenforwards the call to the cellular Visited Function 274 as a PSTN calldirected towards the RN assigned to the subscriber (i.e., the call isrouted to the cellular Visited Function as a PSTN call based upon thesubscriber's RN), step 8. The PSTN call of step 8 to the cellularVisited Function corresponds to the media leg E of FIG. 12. The cellularVisited Function then forwards the call to the subscriber terminal.

FIG. 13 is a block diagram illustrating an example delivery of a PSTNcall to a Mobile IP-telephony subscriber roaming to a cellular network.The call delivery in FIG. 13 is very similar to that of FIGS. 11 and 12,with the following differences. The PSTN call is directed to thestandard IP-telephony Gateway 211 at leg X, which is a standardIP-telephony gateway having no mobility support. The standardIP-telephony Gateway 211 then takes the place of the calling entity inFIG. 11. The standard IP-telephony Gateway 211 statically translates theMSISDN to obtain the IP address of the MIPTN Home Function 204. Thestandard IP-telephony Gateway 211 then queries the Home Function 204 toobtain the IP address where the subscriber can be reached, which is theIP address of the Gateway Function 210. The media of the call is thenrouted through the Gateway Function 210 to the cellular Visited Function274. The remaining steps are the same as FIGS. 11 and 12.

There are three ways in which the functionality of Gateway Function 210and standard IP-telephony Gateway 211 can be provided in FIG. 13. First,a Gateway Function 210 and standard IP-telephony Gateway 211 can be usedas shown in FIG. 13. Second, the function of the standard IP-telephonyGateway 211 can also be provided by the Gateway Function 210 (which alsohas mobility support, such as dynamic mapping which is not provided ingateway 211). In this second embodiment, there would only be one Gatewayused (i.e., Gateway Function 210) because standard IP-telephony Gateway211 is now unnecessary. In a third embodiment, two Gateway Functions 210would be used (one Gateway Function 210 replacing the Gateway 211 inFIG. 13).

FIG. 14 is a diagram illustrating an example delivery of an IP-telephonycall to a mobile cellular network subscriber roaming to an IP-telephonynetwork. FIG. 15 is a block diagram illustrating an example delivery ofan IP-telephony call to a mobile cellular network subscriber roaming toan IP-telephony network, corresponding to FIG. 14. In FIGS. 14 and 15,it is assumed that the cellular subscriber has already contacted aserving MIPTN Visited Function 206 to register as described in FIG. 8.As part of the registration, the Gateway Function 210 has stored adynamic correspondence between the called subscriber's IMSI and thetransport address of the MIPTN Visited Function where the subscriber hasregistered (i.e., where the subscriber is located). The subscriber'scellular Home Function (i.e., HLR 264) also has stored the GatewayFunction number of Gateway Function 210 (in E.164 format or othertelephony/PSTN format) corresponding to the IMSI.

In step 1 of FIG. 14, a call setup/address request message is routed asan IP-telephony message or procedure from the calling entity to thestandard IP-telephony Gateway 211 (or alternatively, to the GatewayFunction 210), based on the dialed MSISDN. The message of step 1corresponds to signaling leg A of FIG. 15.

The standard IP-telephony Gateway 211 receives the call setupmessage/address request. The MSISDN in the call setup message identifiesa cellular subscriber. Therefore, the subscriber's MSISDN points to thecellular Home Function 266 (i.e., MSISDN points to HLR 264/GW MSC 262).Thus, at step 2 of FIG. 14, the standard IP-telephony Gateway 211 sendsa route request message to the cellular Home Function 204 based on theMSISDN, providing the called subscriber's MSISDN (or other subscriberidentification or subscriber ID). The message of step 2 is an example ofthe signaling provided on leg B of FIG. 15.

The cellular Home Function 266 receives the Route request message. TheGW MSC 262 (of the cellular Home Function 266) then queries orinterrogates the HLR 264 to obtain the current location information forthe called subscriber. The HLR 264 returns the Gateway Function numberof Gateway Function 210 (in E.164 format), where the subscriber can bereached. Cellular Home Function also identifies the IMSI correspondingto the MSISDN. At step 3 of FIG. 14, the cellular Home Function 266sends a roaming number (RN) request message to the Gateway Function 210,providing the called subscriber's IMSI. The message of step 3 (FIG. 14)is an example of the signaling provided on leg C of FIG. 15.

The Gateway Function 210 receives the RN request message, including theIMSI. From registration, the Gateway Function 210 stores acorrespondence between the subscriber's IMSI and the transport addressof the Visited Function where the subscriber can be reached (e.g., VF_TAor CCEVF_TA). At step 4 of FIG. 14, the Gateway Function 210 sends astatus enquiry message to the MIPTN Visited Function 206 (if necessary),and receives a status response at step 5. The MIPTN Visited Function maysimilarly send a status enquiry message to the called subscriberterminal, and receive a status response therefrom. The messages of steps4 and 5 (FIG. 14) are examples of the signaling provided on leg D ofFIG. 15.

The Gateway Function 210 receives the status response message of step 5of FIG. 14. If the subscriber terminal is reachable or able to receivethe call, the Gateway Function 210 assigns a roaming number (RN) to thesubscriber terminal, and stores the correspondence between the IMSI andRN. (The Gateway Function has already stored the correspondence betweenthe IMSI and the VF_TA where the subscriber is registered or located).At step 6 of FIG. 14, the Gateway Function sends a RN response messageto the cellular Home Function 266, providing the RN assigned to thecalled subscriber. The message of step 6 is an example of the signalingof leg C of FIG. 15.

Steps 7-11 of FIG. 14 will be briefly explained, and provide additionalexamples of call control signaling. At step 7 of FIG. 14, the cellularHome Function 266 sends a call setup message to the Gateway Function210, based on the RN (i.e., message is routed to Gateway Function 210based on the RN). The Gateway Function 210 uses the dynamiccorrespondence tables to identify the IMSI corresponding to the RN, andthen identify the transport address of the MIPTN Visited Function (e.g.,VF_TA or CCEVF_TA) corresponding to the IMSI. At step 8 of FIG. 14, theGateway Function then sends a call setup message to the VF_TA (or to theCCEVF_TA), providing the IMSI as an alias. At step 9 of FIG. 14, theMIPTN Visited Function sends a call setup message to the subscriberterminal (MS), over whatever linkage or type of access that is used bythe subscriber terminal (e.g., IP-telephony, ISDN, radio or cellular).There would be acknowledgments to each of messages of steps 7, 8 and 9,but are not shown. At step 10 of FIG. 14, the cellular Home Functionsends an acknowledgment for call setup back to the standard Gateway 211,which in turn also issues an acknowledgment at step 11. The messages ofsteps 7-11 are simply examples of the types of signaling which may occurbetween the entities.

At step 12 of FIG. 14, the calling entity sets up an IP-telephony calltowards the standard IP-telephony Gateway 211, and may provide thecalled subscriber's MSISDN as an alias. The call of step 12 (FIG. 14)corresponds to the call provided on leg E of FIG. 15. At step 13 of FIG.14, the standard IP-telephony Gateway 211 forwards the call as PSTN callbased on the MSISDN to the cellular Home Function 266 (i.e., the call isrouted to the GW MSC 262). The call of step 13 (FIG. 14) corresponds tothe call of leg F in FIG. 15.

At step 14 of FIG. 14, the cellular Home Function 266 identifies theIMSI corresponding to the MSISDN (static correspondence), and thenidentifies the RN corresponding to the IMSI (dynamic correspondence).The cellular Home Function 266 (in particular, the GW MSC 262) thenforwards the call as a PSTN call to the Gateway Function 210 based onthe RN assigned to the subscriber. The call of step 14 (FIG. 14)corresponds to leg G of FIG. 15.

At step 15 of FIG. 14, the Gateway Function 210 identifies the IMSIcorresponding to the RN, and then identifies the VF_TA (or CCEVF_TA)corresponding to the IMSI (both are dynamic). The Gateway Function 210then sets up an IP-telephony call towards the address of the MIPTNVisited Function where the subscriber is located (where subscriber isregistered). As part of the IP-telephony call setup, the parties maynegotiate the address at the Visited Function that will receive thevoice media (i.e., packetized voice). This transport address of theMIPTN Visited Function may be referred to herein as, for example, theRTP_TA (or the VF_TA if one address is used for signaling and media).This IP-telephony call of step 15 (FIG. 14) corresponds to media leg Hof FIG. 15.

At step 16 of FIG. 14, the MIPTN Visited Function forwards the receivedcall to the subscriber terminal (if Visited Function is separate fromthe subscriber terminal). The call can be forwarded to the subscriberover whatever linkage or type of access that the subscriber terminal isusing, such as IP-telephony call, an ISDN call, a cellular call, etc.Steps 12-16 may be performed in an order other than what is shown inFIG. 14.

In an alternative embodiment, only one Gateway is used (Gateway Function210), because Gateway Function 210 can also perform the functions of thestandard IP-telephony Gateway 211. Thus, replacing the standardIP-telephony Gateway 211 and the Gateway Function 210 in FIG. 15 with asingle Gateway Function 210 can simplify call delivery.

FIG. 16 is a block diagram illustrating an example delivery of a PSTNcall to a mobile cellular network subscriber roaming to an IP-telephonynetwork. The delivery of a PSTN call to a cellular subscriber that isroaming in the MIPTN 202 (FIG. 16) is very similar to the delivery of aIP-telephony call to a cellular subscriber that is roaming in theIP-telephony network (FIGS. 14 and 15). Referring to FIG. 16, the PSTNcall is routed based on the dialed MSISDN to the cellular Home Function266 directly (rather than through a Gateway). The structure andoperation of the remainder of FIG. 16 is similar to the call deliverysteps illustrated in FIGS. 14 and 15.

Short Message Service (SMS)

As provided in GSM, Short Message Service (SMS) gives mobile phonesubscribers the ability to send and receive short text messages. Shortmessages usually contain about one page of text or less. Some systemslimit the short message to 160 alphanumeric characters. However, thereis presently no provision for providing short messages over anIP-telephony network, or to subscribers roaming between a cellularnetwork and an IP-telephony network. The present invention includesfeatures for delivering short messages over an IP-telephony network(e.g., over MIPTN 202), and for delivering short messages to subscribersroaming between cellular network 260 and MIPTN 202.

FIG. 17 is a diagram illustrating an example delivery of a short messagefrom a IP-telephony short message service center to a mobile cellularnetwork subscriber that is roaming within the cellular network. FIG. 17assumes that the cellular network subscriber has already registered withthe serving cellular Visited Function. A message can be generated from ashort message terminal (SMT) 720 or other computer or terminal. Themessage from the SMT 720 is delivered over line 722 to the MIPTN ShortMessage Service center (SMSC) 420, along with an alias identifying thedestination or target subscriber, such as a MSISDN (or other subscriberidentification). Alternatively, the short message can be generated andprovided from a subscriber terminal (either a MIPTN subscriber or acellular subscriber) that is registered with MIPTN Visited Function 206.In such case, the MIPTN Visited Function 206 forwards the short messageand the MSISDN (or other subscriber identification) that identifies thetarget or destination subscriber for the message. Because the targetsubscriber is a cellular network subscriber, the subscriber's MSISDNpoints to a Gateway Function 210 (FIG. 5). The SMSC 420 sends an addressrequest message to the SMS GW 630 of the Gateway Function 210, includingthe MSISDN of the target subscriber. The address request message of step1 is directed to the SMS GW630 because it is signaling for a shortmessage.

In the cellular network 260, the cellular subscriber's MSISDN points tothe cellular Home Function 266 (e.g., HLR 264). Based on the MSISDN, theSMS GW 630 sends a route request message at step 2 of FIG. 17 as acellular procedure or message to the HLR 264, based on the MSISDN,providing the MSISDN.

The HLR 264 stores a static correspondence between the subscriber's IMSIand MSISDN, and a dynamic correspondence (from registration) between thesubscriber's IMSI and the VLR number (in E.164 format) identifying theserving VLR where the subscriber is located. Thus, the HLR identifiesthe IMSI corresponding to the MSISDN, and then the VLR numbercorresponding to the IMSI of the destination subscriber. At step 3 ofFIG. 18, the HLR sends a route response message to the SMS GW 630,providing the IMSI and VLR number (in E.164 format). The SMS GW alsostores the dynamic correspondence between the VLR number and thedestination subscriber's IMSI.

At step 4 of FIG. 17, the SMS GW 630 sends an address response messageas an IP-telephony message or procedure to SMSC 420, providing the IMSIand the transport address (e.g., IP address and port number) of the SMSGW 630 (SMSGW_TA).

At step 5 of FIG. 17, the SMSC 420 sends a forward short message (FSM)message as an IP-telephony message to SMS GW 630, providing the IMSI ofthe destination subscriber and the short message (msg).

The SMS GW 630 receives the FSM message of step 5. The SMS GW 630identifies the VLR number (in E.164 format) corresponding to the IMSIusing the dynamic correspondence just stored in response to step 3.Because FIG. 17 involves a cellular subscriber roaming within a cellularnetwork 260, no dynamic correspondence was stored in any GatewayFunction 210 during cellular subscriber registration.

At step 6 of FIG. 17, the SMS GW 630 then sends a FSM message as acellular procedure or message to the identified (serving) VLR number,providing the subscriber's IMSI and the short message.

At step 7 of FIG. 17, the serving VLR then sends a message as a cellularmessage or procedure to deliver the short message to the destinationsubscriber terminal 750, where the message can be output on thesubscriber terminal 750 (e.g., displayed, printed).

Steps 8-10 of FIG. 17 are acknowledgment messages. At step 8 of FIG. 17,the terminal 750 sends a message back to the serving VLR as anacknowledgment of receiving the short message. At step 9, the servingVLR sends an acknowledgment message back to the SMS GW 630. The SMS GW630 then deletes the dynamic correspondence between the IMSI and the VLRnumber from the GWDB 634. At step 10 of FIG. 17, the SMS GW 630 sends anacknowledgment message back to the SMSC 420. The SMSC 420 may also thensend an acknowledgment back to the SMT 720 or the Visited Function 206that sent the short message.

FIG. 18 is a diagram illustrating an example delivery of a short messagefrom a cellular short message service center to a mobile MIPTNsubscriber that is roaming within the MIPTN network. FIG. 18 issymmetric to FIG. 17, but includes a cellular SMSC 900. The cellularSMSC 900 is connected to the cellular network 260 and/or the PSTN 240.In FIG. 18, the subscriber's Home Function is a MIPTN Home Function 204,and the subscriber is located at MIPTN visited Function 208. In FIG. 18,the SMSGW 630 obtains the IP address of the Visited Function where thesubscriber can be reached, which in this case is a MIPTN VisitedFunction. The short message is then forwarded to the serving VisitedFunction 208 for delivery to the subscriber.

FIG. 19 is a diagram illustrating an example delivery of a short messagefrom an IP-telephony short message service center to a mobile cellularnetwork subscriber that is roaming within the IP-telephony network. FIG.20 is a diagram illustrating an example delivery of a short message froma cellular network short message service center to a mobile IP-telephonynetwork subscriber that is roaming within a cellular network. FIGS. 19and 20 (as with the other message delivery Figures) each assume that thecellular network subscriber has already contacted the appropriateserving Visited Function to perform registration. There may be severalGateway Functions 210 in MIPTN 202. Note that in the examples of FIGS.19 and 20, there are two SMS Gateways (SMS GW1 630 and SMS GW2 630),each residing within a different Gateway Function 210. As a result, eachSMS Gateway also has access to the GWDB 634 in the corresponding GatewayFunction 210 where any dynamic mappings are stored during subscriberregistrations.

In FIGS. 19 and 20, it is assumed that the Gateway Function 210corresponding to SMS GW2 performed registration, thereby storing thedynamic mappings (IMSI to Visited Function address). In general, theGateway Function 210 that was used for subscriber registration orlocation update will rarely be the same one used for short messagedelivery. In the examples of FIGS. 19 and 120, the SMS GW that isclosest to the Short Message Service Center (SMSC) 420 may be used(i.e., SMS GW1) for short message delivery, while SMS GW2 was usedduring subscriber registration.

Thus, in the example of FIG. 19, the number (in E.164 format)identifying SMS GW2 is stored in the HLR as the location where thedestination subscriber can be reached. SMS GW2 also stores duringregistration a dynamic mapping between the subscriber's IMSI and thetransport address of the MIPTN Visited Function 208 where the subscriberis now located. SMS GW1 does not itself maintain the locationinformation corresponding to the IMSI. As a result, SMS GW1 must forwardthe short message to the SMS Gateway that was involved in subscriberregistration (SMS GW2), so the short message can be delivered to thesubscriber.

Referring to FIG. 19, at step 1 the Short SMSC 420 sends an addressrequest message to a SMSGW, such as the closest SMSGW (in this case, SMSGW1). At step 2, the SMS GW1 sends a route request message to the HLR264, providing the MSISDN (because in the cellular network, the MSISDNpoints to the HLR 264 for a cellular subscriber).

In response to the route request message of step 2 (FIG. 19), the HLR264 identifies the location information corresponding to the MSISDN.Thus, at step 3, the HLR sends a route response message to the SMS GW1,providing the IMSI and the number of the SMS GW2 (in E.164 format) atwhich the destination subscriber can be reached. The SMS GW1 then storesthe correspondence between the IMSI and the number (in E.164 format) ofthe SMS GW2, where the destination subscriber can be reached.

At step 4 of FIG. 19, the SMS GW1 sends an address response message tothe SMSC 420, providing the transport address (or IP address) of the SMSGW1 (e.g., SMSGW1_TA), and the IMSI. At step 5 of FIG. 19, the SMSC thensends a forward short message (FSM) message to the SMS GW1, providingthe IMSI and the short message. The SMS GW1 identifies the numbercorresponding to the IMSI, which is the number of the SMSGW2 (e.g., inE.164 format or other cellular/telephony format). At step 6 of FIG. 18,the SMS GW1 then sends a FSM message to SMSGW2 as a cellular procedureor message (based on the number of the SMSGW2 in E.164 format),providing the IMSI of the target subscriber and the short message.

The SMS GW2 identifies the transport address or IP address where thetarget subscriber (i.e., corresponding to the IMSI) can be reached,based on information stored during registration. In this case, the IMSIcorresponds to the transport address of MIPTN Visited Function 208(VF208_TA). At step 7 of FIG. 19, the SMS GW2 sends a FSM message as anIP-telephony message or procedure to MIPTN Visited Function 208 based onthe IP address corresponding to the IMSI, providing the IMSI (ifnecessary) and the message. At step 8, the MIPTN Visited Function thenforwards the short message to the target subscriber terminal 760. Themessages of steps 9-12 of FIG. 19 are acknowledgments.

FIG. 20 is a diagram illustrating an example delivery of a short messagefrom a cellular network short message service center to a mobileIP-telephony network subscriber that is roaming within a cellularnetwork. Short message delivery of FIG. 20 is symmetric to that of FIG.19. As in FIG. 19, here in FIG. 20 it is assumed that SMS GW1 is usedfor short message delivery (but SMS GW1 was not involved in registrationof the target or destination subscriber), and SMS GW2 was involved insubscriber registration. In the case of FIG. 20, in the MIPTN 202, theMSISDN points to the MIPTN Home Function 204. Thus, at step 2 of FIG.20, the SMS GW1 queries the MIPTN Home Function 204 for the subscriberlocation information corresponding to the MSISDN. In this case, thesubscriber location information is the transport address (e.g., IPaddress) of SMS GW2. This address (SMSGW2_TA) is stored in SMS GW 1 ascorresponding to the target subscriber's IMSI. Upon receiving the FSMmessage (including the short message), the SMS GW1 forwards the FSMmessage including the short message to the SMS GW2 based on this IPaddress. The SMS GW2 stores the VLR number of the cellular VisitedFunction (from registration). Thus, at step 7 of FIG. 20, the shortmessage is delivered to the serving cellular Visited Function (e.g., theserving VLR). The short message is then forwarded to the subscriberterminal, step 8.

FIG. 21 is a diagram illustrating an example delivery of a short messagefrom a cellular network short message service center to a cellularnetwork subscriber that is roaming within an IP-telephony network. Atsteps 1 and 2 of FIG. 21, the cellular SMSC 900 obtains from thecellular Home Function (e.g., the HLR 264) the cellular address wherethe subscriber can be reached, which in this case, is the cellularaddress of the SMSGW 630. (Cellular SMSC 900, e.g., is connected to thecellular network 260 and/or PSTN 240). At step 3 of FIG. 21, the shortmessage is forwarded to the SMSGW 630. The SMSGW 630 dynamicallytranslates the subscriber's IMSI to the IP address of the MIPTN VisitedFunction 208 (where the subscriber is located), based on a dynamicmapping stored in the SMSGW 630 during registration. SMSGW 630 thendelivers the short message to the Visited Function 208 for delivery tothe subscriber, steps 4 and 5.

FIG. 22 is a diagram illustrating an example delivery of a short messagefrom an IP-telephony network short message service center to anIP-telephony subscriber that is roaming within a cellular network. Themessage delivery of FIG. 22 is symmetric to the case in FIG. 21. In FIG.22, the MIPTN SMSC 420 obtains the IP address (SMSGW TA) of the SMSGWthrough which the subscriber can be reached. The message is thenforwarded to the SMSGW 630. The SMSGW then uses a dynamic mappingobtained during registration to translate the subscriber IMSI to acellular address of the cellular Visited Function where the subscriberis located. The message is then delivered to the cellular VisitedFunction.

FIG. 23 is a diagram illustrating an example delivery of a short messagefrom an IP-telephony network short message service center to anIP-telephony subscriber that is roaming within an IP-telephony network.At step 1 the MIPTN SMSC 420 sends a message to the MIPTN Home Function204 of the target subscriber (based on the MSISDN), providing theMSISDN. The Home Function 204 then provides the IP address (VF_TA) ofthe MIPTN Visited Function 208 where the subscriber is located. TheMIPTN SMSC then forwards the short message to the MIPTN Visited Function208 for delivery to the subscriber.

FIGS. 17-23 illustrate examples of successful deliveries of SMSmessages. However, in some cases the message delivery may fail (i.e., anunsuccessful message delivery). In the event of a message deliveryfailure, the SMSC stores the message (i.e., continues to store themessage) and the SMSC will attempt delivery later when alerted by thesubscriber's Home Function that the subscriber is available to receivemessages.

The SMSC can be notified of the delivery failure (e.g., through anegative acknowledgment notifying the SMSC of the failure, or by theSMSC's failure to receive an acknowledgment within a predetermine periodoftime). The SMSC then sends a Report Delivery Status (RDS) message tothe destination subscriber's Home Function to report the faileddelivery, providing an MSISDN (or IMSI) of the destination subscriber.The RDS message may be sent through the SMS GW 630 of Gateway Function210 to the Home Function. The SMS GW 630 statically translates theMSISDN to the address of the subscriber's Home Function, and forwardsthe RDS message to the subscriber's Home Function, providing the MSISDNand the address of the SMS GW. The address of the SMS GW 630 is providedto the Home Function so that the Home Function can send an alert messageto the SMSC via the SMS GW to notify the SMSC that the subscriber is nowavailable to receive the messages.

The SMS GW 630 also stores a dynamic correspondence between the MSISDN(identifying the destination subscriber) and the address of the SMSC(identifying the SMSC that has a message to be sent to the subscriber).The SMS GW 630 may in fact store a group of SMSC addresses correspondingto one MSISDN, where each of the SMSCs of the group has a message to bedelivered to the subscriber.

When a subscriber becomes available to receive the message, thesubscriber terminal informs the Visited Function where it is located,and the Visited Function informs the subscriber's Home Function that itis now available to receive messages.

The Home Function then sends an alert message to the SMS GW 630. The SMSGW 630 then uses the dynamic mapping (MSISDN/SMSC address) to identifythe address of the SMSC (or the multiple SMSCs) that have messages tosend to this subscriber. The alert message is then forwarded to each ofthe SMSCs, and each SMSC again attempts to forward the short message tothe subscriber.

Several embodiments of the present invention are specificallyillustrated and/or described herein. However, it will be appreciatedthat modifications and variations of the present invention are coveredby the above teachings and within the purview of the appended claimswithout departing from the spirit and intended scope of the invention.

1. A method of call delivery to a packet-switched telephony subscriberthat is roaming within a packet-switched telephony network comprising:receiving a packet-switched telephony call at a packet-switchedtelephony home function from a calling entity, the call including asubscriber identification identifying the called subscriber; the homefunction identifying subscriber location information including apacket-switched telephony network address of a visited functioncorresponding to the subscriber identification; the home functionproviding the address of the visited function to the calling entity;establishing a packet-switched telephony call from the calling entitytowards the address of the visited function; and the home functioncommunicating with the visited function to determine that the calledsubscriber can receive the call prior to providing the visited functionaddress to the calling entity.
 2. A method of call delivery to apacket-switched telephony subscriber that is roaming within apacket-switched telephony network comprising: receiving apacket-switched telephony call at a packet-switched telephony homefunction from a calling entity, the call including a subscriberidentification identifying the called subscriber; the home functionidentifying subscriber location information including a packet-switchedtelephony network address of a visited function corresponding to thesubscriber identification; the home function providing the address ofthe visited function to the calling entity; establishing apacket-switched telephony call from the calling entity towards theaddress of the visited function; the home function communicating withthe visited function to determine if the called subscriber can receivethe call; and providing the visited function address to the callingentity only if the called subscriber can receive the call; andotherwise, if the called subscriber is unable to receive the call, thehome function returning an address corresponding to the subscriber wherethe calling entity may leave a voice message for the called subscriber.3. A method of call delivery to a packet-switched telephony subscriberthat is roaming within a packet-switched telephony network comprising:receiving a packet-switched telephony call at a packet-switchedtelephony home function from a calling entity, the call including asubscriber identification identifying the called subscriber; the homefunction identifying subscriber location information including apacket-switched telephony network address of a visited functioncorresponding to the subscriber identification; and the home functionproviding the address of the visited function to the calling entity; andestablishing a packet-switched telephony call from the calling entitytowards the address of the visited function, wherein said step ofestablishing comprises the steps of: sending call control signalingbetween the calling entity and the visited function to set up thepacket-switched telephony call; and sending the media of thepacket-switched telephony call directly from the calling entity to thevisited function.
 4. The method of claim 3 wherein said step of sendingcall control signaling comprises sending call control signaling directlybetween the calling entity and the visited function to set up thepacket-switched telephony call.
 5. The method of claim 3 wherein saidstep of sending call control signaling comprises sending call controlsignaling between the calling entity and the visited function throughthe home function to set up the packet-switched telephony call.
 6. Themethod of claim 3 wherein one address at the visited function is usedfor call control signaling and media for the call.
 7. The method ofclaim 3 wherein a first address at the visited function is used for callcontrol signaling to set the call up and a second address at the visitedfunction is used for media of the call.
 8. The method of claim 7 whereinthe second address at the visited function used for call media isnegotiated by the calling entity and visited function using the callcontrol signaling during call setup.
 9. A method of call delivery withina mobile Packet-switched telephony network comprising: receiving a PSTNcall at a gateway function, the call including a subscriberidentification of the called subscriber; the gateway function obtainingfrom the subscriber's packet-switched telephony home function subscriberlocation information for the called subscriber, the subscriber locationinformation including an address of a visited function corresponding tothe subscriber identification; and establishing a packet-switchedtelephony call from the gateway function towards the address of thevisited function; wherein said step of obtaining comprises the steps of:sending an address request message including the called subscriber'ssubscriber identification from the gateway function to the calledsubscriber's home function in the packet-switched telephony network; thehome function identifying subscriber location information including anaddress of a visited function corresponding to the subscriberidentification; and receiving a message at the gateway function from thesubscriber's home function including the address of the visited functioncorresponding to the subscriber identification, and further comprisingthe step of the home function communicating with the visited function todetermine that the called subscriber can receive the call prior to thegateway function receiving the message including the visited functionaddress.
 10. A method of call delivery within a mobile Packet-switchedtelephony network comprising: receiving a PSTN call at a gatewayfunction, the call including a subscriber identification of the calledsubscriber; the gateway function obtaining from the subscriber'spacket-switched telephony home function subscriber location informationfor the called subscriber, the subscriber location information includingan address of a visited function corresponding to the subscriberidentification; and establishing a packet-switched telephony call fromthe gateway function towards the address of the visited function,wherein said step of establishing comprises the steps of: sending callcontrol signaling between the gateway function and the visited functionto set up the packet-switched telephony call; and sending the media ofthe packet-switched telephony call directly from the gateway function tothe visited function.
 11. The method of claim 10 wherein said step ofsending call control signaling comprises sending call control signalingdirectly between the gateway function and the visited function to set upthe packet-switched telephony call.
 12. The method of claim 10 whereinsaid step of sending call control signaling comprises sending callcontrol signaling between the gateway function and the visited functionthrough the home function to set up the packet-switched telephony call.